PlzNavigate: Show error pages when the navigation failed before commit

content/browser/frame_host/navigation_request.cc

Index: content/browser/frame_host/navigation_request.cc
diff --git a/content/browser/frame_host/navigation_request.cc b/content/browser/frame_host/navigation_request.cc
index e5973ee3284556933bebee93e008f511026f5236..f46eecba30ff0f5b1d9a3d4f827d50c90949d76d 100644
--- a/content/browser/frame_host/navigation_request.cc
+++ b/content/browser/frame_host/navigation_request.cc
@@ -203,11 +203,12 @@ void NavigationRequest::OnResponseStarted(
                                                   response.get(), body.Pass());
 }
 
-void NavigationRequest::OnRequestFailed(int net_error) {
+void NavigationRequest::OnRequestFailed(bool has_stale_copy_in_cache,
+                                        int net_error) {
   DCHECK(state_ == STARTED);
   state_ = FAILED;
-  // TODO(davidben): Network failures should display a network error page.
-  NOTIMPLEMENTED() << " where net_error=" << net_error;
+  frame_tree_node_->navigator()->FailedNavigation(
+      frame_tree_node_, has_stale_copy_in_cache, net_error);
 }
 
 void NavigationRequest::OnRequestStarted(base::TimeTicks timestamp) {